This proposal investigates how histone lysine demethylase LSD2 is targeted and retained to actively transcribed gene bodies by its cofactor NPAC. We hypothesize that NPAC has dual interactions with LSD2 via NPAC's linker region and the H3K36me3 histone modification- containing nucleosomes via NPAC's PWWP domain, thereby physically linking LSD2 to H3K36me3-enriched functional sites. We will employ various NPAC mutation and deletion constructs and use molecular biological and biochemical approaches to determine the molecular mechanism underlying NPAC-mediated targeting of LSD2 to its functional sites. Results from the proposed study will offer significant insight into the molecular mechanism by which NPAC contributes to LSD2 mediated gene regulation within actively transcribed gene bodies. If successful, the proposal is expected to offer new insight into our understanding of the role and mechanism of action of cofactors in regulation of histone demethylation, and make significant impact on the advancement of epigenetic gene regulation and chromatin biology. Ultimately, findings from the proposed study will also provide important information for the development of epigenetic-based therapeutics.